Signaling by electromagnetic waves.



R. A. FESSENDEN.

SIGNALING BY ELECTROMAGNETIC WAVES.

APPLICATION FILED APR. 19. 1906.

1 182,003 Patented May 9, 1916.

W W 1w 'EEMMM UNITED STATES PATENT OFFICE.

REGINALD A. FESSENDEN, 0F BRANT ROCK, MASSACHUSETTS, ASSIGNOR, BY MESNEASSIGNMENTS, TO SAMUEL M. KINTNER, OF PITTSBURGH, PENNSYLVANIA, ANDHALSEY M. BARRETT, OF BLOOMFIELD, NEW JERSEY, RECEIVERS.

SIGNALING BY ELECTROMAGNETIC WAVES.

Application filed April 19, 1906.

T 0 all whom it may concern Be it known that I, REGINALD A. FEssEN- DEN,a citizen of the United States, residing at Brant Rock, in the State ofMassachusetts, have inventei a certain and useful Improvement in theArt. of Signaling by Electromagnetic Waves, of which the following is aspecification.

My invention relates to the sending of electrical signals and moreparticularly the generation of electro-magnetic waves for wirelesstelegraphy.

The primary object of the invention is the more eflicient, certain andcontrollable production of oscillations, as hereinafter more fullydescribed and claimed.

In the accompanying drawings forming a part of this specificationFigures 1, 2 and 3 illustrate forms of apparatus for carrying out myinvention.

The use of a spark for signaling by electromagnetic waves is veryobjectionable not only by reason of its inefficiency and consid erablewaste of energy, but also on account of the noise produced and itsinconstancy in operation, the intensity of the signal? varying fromspark to spark. It is also objectionable in that as generally used itgives few impulses of short duration. By my method these objections areovercome, and the waves are produced efliciently without a spark gap.

In Fig. 1 is shown an induction coil having a core 1, a secondary coil2, a primary coil 3, a break 4, and a condenser 5 shunted across thebreak. cited by any suitable means as for example by the storagebatteries 6. The secondary coil 2 may have one terminal connected to theaerial and the other grounded as shown.

In the practice of my invention the inductance of the circuit containingthe primary coils is made so as to be large compared with its ohmicresistance when the break 4 is closed. As the storage batteries 6 mayhave high resistance they may be shunted by the condenser 7 The timewhich a current takes to rise in R where L is the coeflicient of selfinduction, and R the resistance.

The natural frequency of an electric osa circuit depends upon the timeconstant Specification of Letters Patent.

The induction coil is ex Patented May 9, 1916.

Serial No. 312,724.

cillation depends upon the factor of /LC where L is the coefficient ofself induction and C the capacity.

I so proportion the self induction of the pr mary 3, the ohmicresistance R of the circult when the break 4 is closed, and the capacityof the condenser 5, that the current in 3 rises to the desired valueduring the time of closure of the break 4, and so that on the opening ofthe break, the natural period of the inductance 3 and capacity 5 is suchas to generate oscillating currents of the desired frequency in theantennae, and thereby radiate electromagnetic waves. It is preferred tohave the frequency of the circuit 3, 5, 6 equal to the natural frequencyof the antennae circuit consisting of the antennae, the secondary 2 andground, and this 18 preferably done by adjusting the condensers 8, 5 and7, all of which are perferably variable.

In order to make a sharp break it is preferred to inclose the break 4 incompressed air as shown, as I have found that by this means the break ismade much more sharp and a much higher voltage can be produced.

In Fig. 2, is shown another form in which 9 is an inductance, 10 arotating commutator revolving in compressed air, 11 a brush bearing onthe commutator, 12 and 13 condens-' 15 is an air cuit 9, 13, 10 ispreferably made such that pacity 12 or the capacity 5 is short circuit-'ed, and that when the circuit controllers are open the capacity 12is inseries with the inductance 9 and the capacity 5 is in series with theinductance 3.

Antennae 16 16 alternately may be connecteither directly as through theinductance 9 and grounded, or inductively through the. secondary 17 andgrounded as shown. With an ordinary induction coil it is found that thefrequency of the oscillations of the pri mary circuit will not, as arule exceed 10,000 per second.

For the efficient generation of electromagnetic waves it is found inpractice that theheight of the antennae should not be less than 5 of thewave length and hence with an ordinary type of induction coil theantenna: would have to be approximately 3,000 ft. high for the mostefiicient operation. In the practice of my invention, however, I soproportion the inductance of the primary and the capacity across thebreak that frequencies as high as 100,000 may be obtained in which caseantennae 300 ft. more or less high give very efficient radiation. Ialso, prefer to adjust the capacities and inductance in the primary orantennae circuits so that the antennae circuit is resonant with theprimary circuit, thereby obtaining ,an increase in efficiency. I alsoprefer to have as many breaks per second as possible.

I claim herein as my invention:

1. In apparatus for generating high frequency oscillations, thecombination of an inductance, a circuit controller, a source of current,and a capacity, said capacity being connected so as to be shortcircuited when 1 the circuit controller is closed, and in series. withthe inductance when the controller is and a capacity in shunt to thecurrent source.

3. Apparatus for generating high frequency electrical oscillationsdirectly from a current source comprising a closed oscillating circuitincluding an inductance, two

condensers, a current source shunting one.

of said condensers and a circuit controller,

intermittently shunting the other condenser, substantially as described.

4. Apparatus for generating high frequency electrical oscillationscomprising an antenna-to-ground circuit containing a capacity andinductance, a local closed circuit including said inductance andcapacity and also a current source shunted by another capacity, combinedwith a circuit controller operating to alternately connect the capacityin the antenna in series and in shunt in the antenna at high frequency.

In testimony whereof, I have hereunto set my hand.

REGINALD A. FESSENDEN.

Witnesses:

ROBT. S. KEARNEY, DARWIN S. WOLCO'IT.

